To develop and quantitate standardized maneuvers to stimulate renin secretion in the isolated, perfused kidney. To utilize for the purpose described above, stimuli which affect primarily or exclusively a) baroreceptors (decreased renal perfusion pressure with ureteral occlusion), b) macula densa sodium receptors (changes in sodium concentration of perfusate with constant perfusion pressure, c) intrarenal vascular resistance (theophylline with constant perfusion pressure, with and without ureteral occlusion in order to quantitate the contribution of the macula densa), and d) specific intrarenal receptors (gamma- and B-adrenergic agonists with constant perfusion pressure). To analyze, with the use of specific gamma- and B-adrenergic blockers, a) whether the intrarenal receptor for renin release is a gamma or a B receptor, and b) the extent to which gamma or B adrenergic receptors are involved in the renin release secondary to stimulation of baroreceptors, sodium sensors (macula densa), and renal vascular resistance. To ascertain the influence of calcium on renin release, and to analyze the mechanism by which potassium influences renin secretion.